Remember the housings I kept referring to as the Keck Telescopes? This is a 6-shot panorama from inside the Keck Visitor's Galley. With the workman there, you get some idea of the size. The actual 10-meter mirror of the Keck is composed of several smaller hexagonal sections hydraulically-controlled to keep them in near-perfect alignment. You can see the hexagonal superstructure beneath the mirror just beyond, above, and to your right from the man.